Equestrian safety research: What kind of rider falls and doesn't feel it?

Researchers use auto-industry engineering technology to simulate horse kicks and rider falls.
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Fran Jurga
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Researchers use auto-industry engineering technology to simulate horse kicks and rider falls.
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Crash test dummies were once big news. The American auto industry developed various versions of everything from simple mannikins to sophisticated robots to test the potential for injury to humans behind the wheels of cars when they hit a stationary object, or were hit by a moving object. They starred in commercials. They not only improved safety, they made drivers confident that, if they were behind the wheel of the right car, they might survive a crash.

Those old crash test dummies are out of work now. They're probably stuffed with mothballs, or lying wedged behind the wheel in museum exhibits while they wait for a PIXAR film to bring them back to life. The science of computer modeling means that dummies are virtual heroes instead of disposable ones.

Even though the original crash test dummies couldn’t ride a horse, their equestrian equivalents have been used to test everything from helmets and safety vests to stirrups. Scientists developed horseshoes with sensors to measure impact, and calibrated cameras to capture gait elements or identify lameness. Dummies were strapped into saddles of real and mechanicals horses.

But that was then. We now have the ability to design equestrian bodies and horse limbs by means of finite element analysis (FEA), a computer model that creates a horse that doesn’t need to be led in a straight line and a rider who always keeps his or her weight equal in both stirrups.

Researchers at the University of California at Davis tested computer model results with actual experimental data to evaluate computer use when testing how horse limbs interact with racetrack surfaces. (UC Davis image)

Researchers at the University of California at Davis tested computer model results with actual experimental data to evaluate computer use when testing how horse limbs interact with racetrack surfaces. (UC Davis image)

We’ve seen FEA used in tests for concussion and traumatic brain injury simulations and equipment tests, but new advances are looking at the whole equestrian to examine what types of impacts (a horse kick or a fall from the saddle?) are most dangerous to riders, and what equipment and materials best protect us in different types of impact injuries.

Let's face it, no two rider falls are the same. Equestrians tend to have different types of falls compared to jockeys, and even jockeys have different types of injuries depending on the surface they race on, and if they are flat racing or jump racing. But the impact of a flying hoof varies on what part of your body is in its path, no matter what type of horse is attached to the hoof. But how can the potential for injury be measured?

Swedish researchers tested the effects of a horse's hoof (red ellipse) when a rider is caught beneath the horse. Hoof angle makes a difference.

Swedish researchers tested the effects of a horse's hoof (red ellipse) when a rider is caught beneath the horse. Hoof angle makes a difference.

Researchers at the Chalmers University of Technology’s Centre for Sports and Technology in Sweden is interested in what happens to riders in accidents, and what materials stand up to equestrianism’s challenges. Last week they published the findings of their pilot study, Explicit Finite Element Methods for Equestrian Applications, in the engineering journal Procedia Engineering’s special issue, The Engineering of SPORT. The issue covers research presented at the 11th conference of the International Sports Engineering Association, held in Delft, The Netherlands in July.

In the same issue of the journal, American researchers at the University of California at Davis detailed their computer programming expertise at creating a virtual interaction between galloping racehorses and track surfaces. Modelling the interaction between racehorse limb and race surface by Jennifer Symons, David Hawkins, David Fyhrie, Shrinivasa Upadhyay, and Susan Stover compared computer-simulation results with distal forelimb motions of actual galloping racehorses on mechanically measured race surfaces. 

What happens when a rider falls from a horse and hits the ground at different angles? Computer models measure the potential for injury right down to the number of ribs at risk for fracture.

What happens when a rider falls from a horse and hits the ground at different angles? Computer models measure the potential for injury right down to the number of ribs at risk for fracture.

The university’s team re-purposed virtual auto crash test dummy coordinates sourced from Toyota (technically known as human body models or HBM) and transformed them into equestrians in their software, renaming the models THUMS. Computer simulations of a generic safety vest, a rotationally-falling horse (called "the horse impactor) and a well-aimed hoof were developed to interact with the THUMS coordinates. The risk of chest injury was evaluated with stresses and strains measured for each rib and chest deformation.

Look out! Here comes the hoof! The researchers simulated hoof impacts from both a trampling-type injury and a direct kick to the chest. They were able to vary both the speed of the impact of hoof-meets-human and the direction and impact site.

The computer-simulated equestrians performed admirably. The research’s ultimate conclusion is that FE HBMs/THUMS have the potential to improve equestrian safety and that further studies on equestrian safety-vest designs are warranted.

The computerized crash test dummies in the Swedish research wore computerized safety vests.

The computerized crash test dummies in the Swedish research wore computerized safety vests.

The following results were obtained for each question the researchers hypothetically posed:

1. When a rider is trampled by a horse, how does the risk of injury vary with chest impact location?

The risk of injury was higher for hoof impacts close to the sternum compared to more lateral locations that had up to 25% less risk. Hence, this knowledge could be used to optimize novel safety-vest designs with HBM simulations.

2. Does a safety-vest provide protection if the rider is kicked by a horse and does the protection vary with the violence of the hoof impact?

Yes, the safety-vest provided protection against horse kicks, and it varied with the violence of the kick. Therefore, if the range of impact energy that occurs in real-world accidents is known, HBM simulations can be used to optimize the vest material properties.

3. Can a safety-vest provide any benefit when the rider is hit by the horse after a rotational fall?

No, the safety-vest (tested) did not provide any benefit when the horse lands on top of the rider. This conclusion suggests that safety measures should focus on preventing this type of accident, rather than designing personal protection for the rider.

4. How does the risk for thoracic (chest) injuries vary when the rider falls off at different angles?

When the rider falls with the head first, the number of predicted rib fractures increases compared to flat falls. However, the model predicts rib fractures for all of the falls simulated from a height of 1.5 meters for a rider without a safety vest.

The Chalmers research, and all the papers from the ISEA 2016 Conference are freely available online under an Open Access license, thanks to Procedia Engineering (Elsevier) and ISEA.

Citations:
Explicit Finite Element Methods for Equestrian Applications, 
Karin Brolin, Jacob Wass,
Procedia Engineering, Volume 147, 2016, Pages 275-280, ISSN 1877-7058, http://dx.doi.org/10.1016/j.proeng.2016.06.277.

Modelling the Interaction Between Racehorse Limb and Race Surface,
Jennifer Symons, David Hawkins, David Fyhrie, Shrinivasa Upadhyaya, Susan Stover, 
Procedia Engineering, Volume 147, 2016, Pages 175-180, ISSN 1877-7058, http://dx.doi.org/10.1016/j.proeng.2016.06.209.